1. Field of the Invention
This invention relates to hypodermic syringes and is related more specifically to a hypodermic syringe having means for retracting the needle, after use, from a working position outside of the barrel of the syringe to a disposal position within the barrel, to avoid inadvertent contact of an operator with the used needle.
2. Description of the Prior Art
Shielding of needles of used hypodermic syringes is generally known. In U.S. Pat. No. 4,425,120, issued Jan. 10, 1984, in the names Norma A., Sampson, et there is disclosed a syringe having a tubular needle guard slidably mounted on the barrel, such that the guard may be moved to an extended position in which the guard shields the needle and to a retracted position in which the guard does not shield the needle.
Other patents showing syringes having tubular needle guards slidable on the syringe barrel from a position removed from the needle to a position covering the needle include U.S. Pat. No. 4,631,057, issued Dec. 23, 1986, in the name of Charles B. Mitchell; U.S. Pat. No. 4,723,943, issued Feb. 9, 1988, in the name of John E. Spencer; U.S. Pat. No. 4,737,144, issued Apr. 12, 1988, in the name of Pradip V. Choskie; U.S. Pat. No. 4,738,663, issued Apr. 19, 1988, in the name of David B. Bogan; U.S. Pat. No. 4,826,491, issued May 2, 1989, in the name of James E. Schramm; U.S. Pat. No. 4,846,796, issued Jul. 11, 1989, in the name of Michael W. Carrell, et al.; U.S. Pat. No. 4,874,383, issued Oct. 17, 1989, in the name of R. David McNaughton; and U.S. Pat. No. 4,943,282, issued Jul. 24, 1990, in the names of Mary J. Page, et al.
While the syringes of the type covered by the above patents provide means for shielding a syringe needle after use, the use of a sleeve slidable upon the syringe barrel renders the syringe, in the needle-exposed condition, necessarily larger in diameter than would be the case with the barrel only, resulting in a bulkier tool for hand manipulation. In the needle-covered condition, the length of the barrel is substantially doubled by the extended position of the shielding sleeve, resulting in a bulkier package to be disposed of.
It would be beneficial to have available a hypodermic syringe having facility for safely shielding the used needle of the syringe, but not with the attendant bulkiness, both during use and in disposal, of the shielding guard sleeve known in the art.